Method for pumping a liquid, pumping station, and pumping area

ABSTRACT

Pumping method, pumping station, and pumping area Method for pumping liquid from a spent liquid pipeline ( 10 ) and comprising the steps of: providing a first pump ( 501 ), providing a junction pipeline ( 15 ), mechanically coupling said junction pipeline ( 15 ) to said first pump ( 501 ) and to said spent liquid pipeline ( 10 ) for allowing liquid to flow from said spent liquid pipeline ( 10 ) to said first pump ( 501 ). The method is characterized in that said first pump ( 501 ) is a self-priming pump.

The invention relates to the technical field of pumping stations andpumping areas for liquid. More specifically, the invention relates,according to a first aspect, to a method for pumping liquid. Accordingto a second aspect, the invention relates to a pumping station, andaccording to a third aspect, to a pumping area.

STATE OF THE ART

FR2837244 describes a pumping station which can be used to pump or raisespent waters from connecting underground pipelines to the surface of theground. This pumping station comprises one (or more) pump(s) which is(are) housed in a tank. This tank comprises an inlet opening into whichis introduced an intake pipeline (or spent liquid pipeline) conveying,for example, spent waters from a gravity network. The spent watersleaving the intake pipeline are poured into a main duct towards the pumpor pumps which can direct these waters by pumping to an outlet pipeline.

The pumping method and the pumping station of FR2837244 present somedrawbacks. It is fairly complex to use; its incorporation in a pumpingarea is also fairly complex; finally, its incorporation in a pumpingarea is costly.

SUMMARY OF THE INVENTION

According to a first aspect, one aim of the invention is to provide amethod for pumping liquid that is simpler, that is less costly, andwhose implementation in a pumping area is simpler. To this end, theinventors propose a method for pumping liquid from a spent liquidpipeline comprising a spent liquid inlet and a spent liquid outlet andconfigured in such a way that said liquid can flow from said spentliquid inlet to said spent liquid outlet by gravity, said methodcomprising the following steps:

-   -   providing a first pump for pumping said liquid, comprising an        inlet for liquid to be pumped and an outlet for pumped liquid;    -   providing a junction pipeline comprising a first and a second        end;    -   mechanically coupling said first end of said junction pipeline        to said inlet of said first pump and mechanically coupling said        second end of said junction pipeline to said spent liquid outlet        of said spent liquid pipeline such that said inlet for liquid to        be pumped of said first pump is connected to said spent liquid        pipeline via said junction pipeline;        said method being characterized in that said first pump is a        self-priming pump.

The first pump is a self-priming liquid pump. Preferably, this firstpump is a self-priming centrifugal pump. That makes it possible to havehigh pumping flow rates which is often required for raising spentwaters. A self-priming centrifugal pump is also less costly than othertypes of self-priming pumps which makes it possible to reduce the costs.Another example of a first self-priming pump is a positive displacementself-priming pump. Preferably, said first pump is then a peristalticpump or a lobe pump.

A self-priming pump is known by the one skilled in the art. It isdifferentiated from load pumps as described in FR2837244. A self-primingpump is equipped with an automatic mechanism which enables the pump tobe automatically primed. Examples of self-priming pumps are wet primingcentrifugal pumps and dry priming centrifugal pumps. Commercial examplesof self-priming pumps are the CORNELL brand ‘Redi-prime’ and‘venturi-prime’ pumps, the Godwin brand ‘dri-prime’ pumps or even theGorman-Rupp brand ‘priming assist’ pumps. For the wet primingcentrifugal pumps, the volute of the pump is surrounded by an outerjacket which serves as a liquid tank. There is a passage between thevolute and the liquid tank which is used to create the vacuum in thesuction piping. For the dry priming centrifugal pumps, the liquidcentrifugal pump is twinned with a vacuum pump which makes it possibleto create the vacuum in the suction piping, thus enabling the liquidpump to be primed.

The priming of a pump for liquid is a concept known to those skilled inthe art. The priming is necessary to enable the liquid to be pumped by apump for liquid. It describes the filling of a pump by the liquid to bepumped after removal of air from the body of the pump and in theupstream piping (or suction duct) which should bring the liquid to bepumped to the pump. A pump without automatic priming cannot on its owndischarge the air from the suction duct.

The pump of FR2837244 is not self-priming. In fact, line 11 of page 12reads as follows: the priming of the pumps takes place automatically assoon as the liquid/gas mixture reaches a sufficient density, by virtueof degassing chambers, not represented, situated behind the impellers.Thus, it is essential for the liquid/gas mixture to reach a sufficientdensity for the priming of the pump of FR2837244 which is not the casewith the first self-priming pump of the invention. By using the methodof the invention, there is no need for degassing chambers because thefirst pump is a self-priming pump. Thus, the method of the invention issimpler.

The first pump is self-priming. Priming is therefore possible even ifthe first pump is located at a higher level than the level of liquid tobe pumped. This is not possible with the pump of FR2837244 which is anon self-priming dry bilge pump. This explains why the pump of FR2837244is housed in a bottom portion of a tank to make it possible to createthe conditions necessary for the priming of the pump, namely that thelevel of water in the suction manifold of the impeller of the pump ofFR2837244 is higher than the level at which the centrifugal impeller ofthe pump is located. In particular, this document teaches placing thepump in the low part of said tank (that could also be called dry dock),at the level of the inlet opening through which the intake pipelinearrives and therefore the liquid to be pumped. Thus, in normalconditions of use, the priming of the pump is possible by virtue of theweight exerted by the column of water upstream of the pump. ‘Normalconditions of use’ should be understood to mean conditions correspondingto the case where the water flows from the intake pipeline to the tankby gravity.

Since the priming of the first pump is possible even if the latter islocated at a higher level than the level of liquid to be pumped,incorporating it in a pumping area is simplified: the constraint on thevertical positioning of the pumps of FR2837244 is eliminated (the pumpsof FR2837244 have to be located under the level of water to be pumped toenable them to be primed). Furthermore, it is possible to position thefirst pump of the invention on the surface of the ground even if thespent liquid pipeline is underground (which is generally the case). Thisalso facilitates the implementation of the method of the invention in apumping area; it is then no longer necessary to provide and construct atank or dry dock to house the pump or pumps. There is therefore asignificant reduction in the cost because this civil engineering work isno longer necessary (this tank can be eliminated which is not mentionedin FR2837244 because the set which is described therein does notcomprise any self-priming pump; the tank is therefore necessary). Also,the maintenance of the pumps is easier when they are incorporated in an‘above-ground’ pumping area, because it is more accessible if it islocated on the surface of the ground (compared to a configuration wherethe pumps are located in a tank). The maintenance costs are thereforealso reduced with the method of the invention. In particular, it is notnecessary to provide a ladder to descend to the bottom of such a tankand it is not necessary to descend to the bottom of a tank to inspectthe condition of the pump or pumps. In some places (for example veryrocky places), hollowing out such a tank can be particularly complicatedand costly.

By using a self-priming pump like the first pump of the method of theinvention, it is also possible to position the pump further away fromthe spent liquid outlet of the spent liquid pipeline (intake pipeline ofFR2837244). The pump of FR2837244 has to be positioned as close aspossible to the inlet opening into which the intake pipeline isintroduced. This constraint is eliminated with the method of theinvention. This aspect also facilitates its implementation in a pumpingarea.

The junction pipeline can consist of a single part, for example a pipe.In another preferred version, the junction pipeline comprises a numberof parts, for example several pipes.

The method of the invention has other advantages. By virtue of thejunction pipeline and the coupling means, it is possible to link theinlet of the first pump to the spent liquid outlet of the spent liquidpipeline. This allows the spent liquid to pass from said spent liquidoutlet to the inlet of the first pump without passing through a wet pit.This particular feature is quite original and runs counter to the usualpractice which has been followed in the field of pumping areas for manyyears.

A wet pit is known to those skilled in the art: it describes a well inwhich spent liquid is stored (such as spent waters) before being pumpedto the surface of the ground. Generally, a wet pit is cylindrical with adiameter that is generally between 1.5 and 5 metres, and with a height(or depth) that is generally between 2 and 8 metres. A wet pit can alsotake the form of a hollow prism with square or rectangular base.

The method of the invention makes it possible to eliminate a wet pitfrom a pumping area. There are various advantages that result from this.The implementation of the method of the invention in a pumping area andthe construction of a pumping area relying on the principles of themethod of the invention are easier because it is not necessary toprovide and create this civil engineering work. The costs linked to theimplementation of the method of the invention in a pumping area and theconstruction of a pumping area relying on the method of the inventionare consequently reduced. The absence of wet pit in which spent liquidsuch as spent waters stagnate also makes it possible to reduce theputrid odours rising to the surface. The comfort of adjoining landownerscan therefore be enhanced by virtue of the method of the invention.Since there is no longer a need for a wet pit in a pumping area, it isno longer necessary to provide a ladder (or hatch covers) for accessthereto. This also generates a cost reduction. The absence of wet pitalso makes it possible to increase the number of terrains likely to beable to accommodate a pumping area: the constraints on the ground thathas to accommodate the pumping area are reduced. Along the same lines,it is possible, by virtue of the method of the invention, to provide forthe construction of a pumping area even in demanding places which is notpossible with a pumping area requiring a wet pit.

Preferably, said spent liquid pipeline is an underground pipeline.Preferably, said underground spent liquid pipeline is a pipeline fordischarging spent liquid from a well. Preferably, said well is a pebbletrap. Preferably, said first pump is controlled as follows:

-   -   when a level of liquid to be pumped is h1 or greater, starting        said first pump and imposing a pumping speed v1≠0 on it;    -   if said liquid level is greater than h2<h1 but less than or        equal to h1, imposing said pumping speed v1 on said first pump        if the latter is in operation;    -   when said liquid level reaches h2<h1, imposing a pumping speed        v2<v1 on said first pump during a time interval ΔT, such that        said liquid level is kept constant;    -   after said time interval ΔT, imposing a pumping speed v3 on said        first pump such that said liquid level reaches a value h3<h2;    -   when said liquid level reaches h3<h2, stopping the first pump.

Preferably, the spent liquid pipeline has a mean inclination of between10° and 50° relative to a horizontal plane such that said spent liquidinlet is situated at a higher level relative to said spent liquid outletin a vertical direction. Preferably, the spent liquid pipeline has amean inclination of between 30° and 45° relative to a horizontal planesuch that said spent liquid inlet is situated at a higher level relativeto said spent liquid outlet in a vertical direction. By imposing suchinclinations on the spent liquid pipeline (between 10° and 50° relativeto a horizontal plane, or more preferably between 30° and 45° relativeto a horizontal plane), problems of decantation of solid particlespresent in the liquid to be pumped can be reduced, even avoided. Whenthe spent liquid pipeline is horizontal, there are risks of decantation,notably when the pump or pumps is (are) stopped. These decantationproblems reduce the pumping capacity and can, ultimately, block saidspent liquid pipeline subsequently preventing any liquid pumping. Byimposing an inclination of said spent liquid pipeline that is greaterthan or equal to 10°, and preferentially, greater than 25°, it ispossible to reduce such risks and provide what the inventors call aself-clearing of the pumping station. Imposing such an inclination ofsaid spent liquid pipeline also makes it possible to increase thereliability of a liquid level regulation.

Preferably, the method comprises a step of positioning the first pump onthe surface of the ground. Then, said first pump is readily accessible,facilitating maintenance. This preferred embodiment also has theadvantage of cancelling the need of an underground dry dock where toplace the first pump.

According to a second aspect, the invention relates to a pumping stationcomprising:

-   -   a spent liquid pipeline comprising a spent liquid inlet and a        spent liquid outlet, and configured in such a way that liquid        can flow (into it) from said spent liquid inlet to said spent        liquid outlet by gravity,    -   a pumping set for pumping said liquid from said spent liquid        pipeline and comprising:        -   a first pump for pumping said liquid, comprising an inlet            for liquid to be pumped and an outlet for pumped liquid;        -   a junction pipeline mechanically coupled to said inlet of            said first pump;        -   coupling means mechanically coupled to said junction            pipeline and suitable for mechanically coupling said            junction pipeline to said spent liquid outlet of said spent            liquid pipeline,            said pumping station being configured such that said spent            liquid pipeline is mechanically coupled (preferably linked)            to said junction pipeline by said coupling means, allowing a            flow of spent liquid from the spent liquid inlet of said            spent liquid pipeline to its spent liquid outlet then to            said junction pipeline and then to said inlet for liquid to            be pumped of said first pump when the latter is operating.

The pumping station of the invention is characterized in that said firstpump is a self-priming pump.

Examples of coupling means are: glue, weld, soldered joint, a flange, abend, a collar, or any matching part making it possible to link a freeend of the junction pipeline to the spent liquid outlet of the spentliquid pipeline. Other examples of coupling means are neverthelesspossible.

Generally, the advantages mentioned in relation to the method accordingto the first aspect of the invention apply also to the pumping station,mutatis mutandis. In particular, the pumping station of the invention issimpler to use and simpler to maintain. Since the first pump is aself-priming pump, there is no need to place it at the bottom of a tankor dry dock. It can notably be placed on the surface which simplifiesthe use and maintenance of the pumping station. Since it is notnecessary to provide a tank or dry dock, the pumping station of theinvention is also less costly. This pumping station does not require thepresence of a wet pit because the first pump is directly connected tothe spent liquid outlet of the spent liquid pipeline. The costassociated with the pumping station can therefore also be reduced forthis reason, as was explained previously. The absence of wet pit alsomakes it possible to reduce the quantity of putrid odours. Theincorporation of the pumping station according to the invention in apumping area is less complex compared with existing pumping stations forthe following reasons. Neither a wet pit, nor a dry dock for placing thepump(s) is required. For these reasons, incorporation of the pumpingstation of the invention in a pumping area is also less expensive.

Preferably, the spent liquid pipeline has a mean inclination of between10° and 50° relative to a horizontal plane such that said spent liquidinlet is situated at a higher level relative to said spent liquid outletin a vertical direction. Preferably, the spent liquid pipeline has amean inclination of between 30° and 45° relative to a horizontal planesuch that said spent liquid inlet is situated at a higher level relativeto said spent liquid outlet in a vertical direction.

By imposing such inclinations on the spent liquid pipeline, problems ofdecantation of solid particles present in the liquid to be pumped can bereduced, even avoided. When the spent liquid pipeline is horizontal,there are risks of decantation, notably when the pump or pumps is (are)stopped. These decantation problems reduce the pumping capacity and can,ultimately, block said spent liquid pipeline subsequently preventing anyliquid pumping. By imposing an inclination of said spent liquid pipelinethat is greater than or equal to 10°, and preferentially, greater than25°, it is possible to reduce such risks and provide what the inventorscall a self-clearing of the pumping station. Imposing such aninclination of said spent liquid pipeline also makes it possible toincrease the reliability of a liquid level regulation. Mean inclinationof the spent liquid pipeline is generally determined as follows. Thespent liquid pipeline generally has a cylinder shape. It is thenpossible to define a main axis, for instance an axis of revolution.Means inclination of the spent liquid pipeline is then defined as theinclination of this main axis relative to a local horizontal plane.

Preferably, said spent liquid pipeline is located underground and thepump or pumps is/are located on the surface of the ground. Access to thepump or pumps is then easier while having a pumping station for pumpingwaters flowing underground.

Preferably, the pumping set of the pumping station comprises:

-   -   a self-priming second pump for pumping said liquid, comprising        an inlet for liquid to be pumped and an outlet for pumped        liquid;    -   a junction pipeline mechanically coupled to said inlet of said        second pump;    -   a coupling means mechanically coupled to said junction pipeline        to mechanically couple said junction pipeline to said spent        liquid outlet of said spent liquid pipeline.

In this preferred embodiment, the pumping set therefore comprises twoself-priming pumps. Thus, the maximum pumping capacity, that is to saythe maximum volume of liquid that can be pumped per unit of time isgreater by using the same type of self-priming pump. This isparticularly useful when large quantities of liquid have to be pumped orwhen liquid flowing at a high flow rate has to be pumped. This preferredembodiment presents other advantages. In particular, the pumpingcapacity of the pumping set is assured even if a pump is stopped. One ofthe two pumps can be stopped for different reasons such as, for example:maintenance servicing of said pump requiring its shutdown; shutdownbecause of failure of said pump or of associated auxiliary services (forexample, power supply outage for said pump). Using two pumps rather thanjust one also makes it possible to increase the life of the pumpsbecause it is possible to operate them alternately, which reduces thestresses imposed on the pumps. To this end, the pumping set of theinvention preferentially comprises a regulation system for alternatingthe operation of the first and second pumps. Having the first and secondpumps operate alternately also makes it possible for them to be worn ina noticeably similar manner (they ultimately run for substantiallyequivalent times) which also facilitates the management of maintenanceof the pumps. When the first and second pumps are made to operatealternately, there are significant pump rotation speed peaks orgradients. These speed peaks make it possible to have sufficient speeds(preferentially greater than 0.6 m/s) in the discharge piping (that isto say the piping connected to the outlets for pumped liquid of thepumps) to carry off sand and other solid particles. Thus, the alternateoperation of the pumps allows for cleaning of the piping.

Preferentially, the junction pipeline has a length of between two andnine metres. Also preferentially, it has a length of between four andsix metres. Even more preferentially, it has a length of seven metres.By using a length greater than or equal to two metres for the junctionpipeline, it is possible to reduce the risks associated with cavitation,even eliminate them. By using a length greater than or equal to twometres for the junction pipeline, it is also possible to remotely sitethe pump or pumps at fairly great distances from the spent liquid outletof the spent liquid pipeline. This makes it possible to place the pumpor pumps at readily accessible places making maintenance of the pumpingset even easier. In particular, with such lengths for the junctionpipeline, it is generally possible to place the pump or pumps on thesurface while providing a connection between them and at the place wherethe effluents arrive. Preferably, the junction pipeline is vertical.

Preferably, the pumping set comprises a regulation system forcontrolling the operation of said first pump as follows:

-   -   when a level of liquid to be pumped is h1 or greater, said        regulation system is suitable for starting said first pump and        for imposing a pumping speed v1 on it;    -   when said liquid level is greater than h2<h1 but less than or        equal to h1, said regulation system is suitable for imposing        said pumping speed v1 on said first pump when it is operating;    -   when said liquid level reaches h2<h1, said regulation system is        suitable for imposing a pumping speed v2 on said first pump such        that v2<v1 during a time interval ΔT such that said liquid level        is kept constant;    -   after said time interval ΔT, said regulation system is suitable        for imposing a pumping speed v3 on said first pump such that        said liquid level reaches a value h3<h2;    -   when said liquid level reaches h3<h2, said regulation system is        suitable for stopping the first pump.        With this preferred embodiment, it is possible to provide        self-clearing or self-cleaning of said spent liquid pipeline, in        particular when the latter is inclined relative to a horizontal        plane such that the spent liquid inlet is at a higher level        relative to the spent liquid outlet in a vertical direction. By        virtue of this preferred embodiment, it is in fact possible to        remove floats and decantation residues from said spent liquid        pipeline. The stopping of the first pump at the level h3 makes        it possible to avoid introducing air during the pumping which is        damaging to the pumps both mechanically and hydraulically        (because air pockets can form in the discharge duct), which will        result in the formation of water hammer (pressure impact upon        the stopping of the pumps). Preferably, v1 and v3 are equal to        the maximum pumping speed of said first pump.

Preferably, the pumping set of the pumping station comprises a bypasspipeline coupled to said first pump to allow for cleaning of a regionsituated in said spent liquid pipeline by diverting at least a portionof liquid pumped by said first pump to said region.

There are various advantages of using such a bypass pipeline. Saidbypass pipeline can first of all be used to discharge air when the firstpump is being primed. Also, said bypass pipeline can be used to clean aninternal region of the spent liquid pipeline by placing one of its endsin said region; the cleaning is ensured by the diversion of at least aportion of liquid pumped by the first pump through said bypass pipeline.Finally, when the first pump is stopped, the bypass pipeline can beopened by a user to drain the entire discharge column in order, forexample, to carry out a maintenance intervention on the discharge duct(which can sometimes cover several kilometres). The discharge duct ispositioned downstream of the first pump (that is to say connected to theoutlet for pumped liquid of the first pump) and is used to discharge thepumped liquid.

Preferably, the pumping set of the pumping station comprises a levelsensor for measuring a liquid level. Preferably, this liquid level is alevel of liquid in the spent liquid pipeline. In another preferredvariant, the liquid level could be a level of liquid in a well (forexample a pebble trap) located upstream of the spent liquid pipeline. Byusing such a level sensor, it is possible to regulate the pump or pumpsby knowing such a level and to provide closed loop regulation.Preferably, said level sensor is a bubbling level sensor comprising abubbling tube.

By controlling the level of liquid to be pumped, for example in thespent liquid pipeline, it is possible to avoid pumping air by stoppingthe operation of any self-priming pump when said level becomes lowerthan a certain low threshold which is to be determined. Controlling alevel of liquid in the spent liquid pipeline allows further improvingself-cleaning and self-clearing of the pumping station.

Preferably, the pumping station comprises at least two spent liquidpipelines. Said first pump can then be connected to each of the spentliquid outlets of said spent liquid pipelines. In an embodimentcorresponding to the case where there are a first and a secondself-priming pumps and two spent liquid pipelines, it is preferable toconnect each of said first and one second pumps to a spent liquidpipeline.

The rate of flow of liquid in the spent liquid pipeline is preferablygreater than or equal to 0.4 m/s, even more preferably, greater than orequal to 0.6 m/s and even more preferably, greater than or equal to1m/s. With these three preferred variants, the risks of decantation inthe spent liquid pipeline are reduced and all the more so as said rateof liquid flow increases. Such liquid flow rates can be obtained in thespent liquid pipeline by imposing on it a certain inclination relativeto a horizontal plane, see above. Generally, an inclination greater thanor equal to 30° relative to a horizontal plane has to be imposed toensure that the rate of liquid flow in the spent liquid pipeline is atleast equal to 0.4 m/s.

According to a third aspect, the invention relates to a pumping areacomprising a pumping station as described previously, and a wellconnected with the spent liquid pipeline via its spent liquid inlet.This pumping area can comprise any preferred embodiment of the pumpingstation of the second aspect of the invention.

Generally, the advantages mentioned in relation to the pumping method ofthe first aspect of the invention and the pumping station of the secondaspect of the invention apply also to the pumping area, mutatismutandis. In particular, the pumping area of the invention is simpler touse and simpler to maintain. Since the first pump is a self-primingpump, it is not necessary to place it at the bottom of a tank or drydock. It can in particular be placed on the surface which facilitatesthe use and maintenance of the pumping area. Since it is not necessaryto provide a tank or dry dock, the pumping area of the invention is alsoless costly. This pumping area does not require the presence of a wetpit because the first pump is directly connected to the spent liquidoutlet of the spent liquid pipeline. The cost associated with thepumping area can therefore also be reduced for this reason, as it hasbeen explained previously. The absence of a wet pit also makes itpossible to reduce the quantity of putrid odours. The advantages linkedto the preferred embodiments of the pumping method of the first aspectof the invention and of the pumping station of the second aspect of theinvention also apply for pumping areas comprising such preferredembodiments.

With the pumping station or the pumping area of the invention, ascreening basket is no longer necessary. In preferred variants of thepumping station or of the pumping area, it would nevertheless bepossible to incorporate one. A screening basket is known to thoseskilled in the art. It makes it possible to retain and therefore filterobjects floating on the surface of the liquid to be pumped, for examplepieces of wood.

For the third aspects of the invention, said spent liquid pipeline canbe connected to a recovery pipeline without using a well such as apebble trap. Liquid can therefore pass from said recovery pipeline tosaid spent liquid pipeline without passing through such a well. Theassociated costs are then all the more reduced. Thus, according to thispreferred variant, the invention relates to a configuration comprisingthe pumping station of the invention, a recovery pipeline and couplingmeans for coupling said spent liquid pipeline and said recoverypipeline.

BRIEF DESCRIPTION OF THE FIGURES

These aspects and other aspects of the invention will be clarified inthe detailed description of particular embodiments of the invention,reference being made to the drawings of the figures, in which:

FIG. 1 shows an example of pumping station of the invention incorporatedin a pumping area;

FIG. 2 shows a possible example of configuration for the spent liquidpipeline;

FIG. 3 shows a preferred embodiment of junction pipelines when thepumping set comprises two pumps;

FIG. 4 shows an example of operating mode of pumps when the pumpingstation comprises two pumps;

FIG. 5 shows a part of a preferred embodiment of the pumping station ofthe invention;

FIG. 6 shows a part of a preferred embodiment of the pumping station ofthe invention;

FIG. 7 shows a part of a preferred embodiment of the pumping station ofthe invention;

FIG. 8 shows a part of a preferred embodiment of the pumping station ofthe invention;

FIG. 9 shows a part of a preferred embodiment of the pumping station ofthe invention;

FIG. 10 shows an example of a spent liquid pipeline having a non-zeromean inclination relative to a horizontal plane;

FIG. 11 shows an example of pumping station of the inventionincorporated in a pumping area;

FIG. 12 shows a preferred embodiment of a well of a pumping areaaccording to the invention.

The drawings of the figures are neither to scale nor in proportion.Generally, similar elements are denoted by similar references in thefigures.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 shows a preferred version of the pumping station 3 according tothe invention, incorporated in a pumping area 8. This pumping area 8comprises a well 4 such as a pebble trap. A pebble trap is known tothose skilled in the art. It is generally a cylindrical cavity with adiameter generally between 50 cm and 2 metres (with a preferred value of1 metre) and with a height that is generally between 50 cm and 9 metres(with a preferred value of 5 metres). Spent liquid (for example spentwaters) is generally brought to a pebble trap 4 via one or more recoverypipeline(s) 40. Preferably, the bottom of the pebble trap 4 is situatedapproximately 1 metre below the intake of said recovery pipeline 40situated at the level of said pebble trap 4. Spent liquid can conveystones, pebbles or particles with a density that is higher than theliquid transporting them. When this spent liquid reaches the pebble trap4, these higher density particles have a tendency to fall to the bottomby gravity. The function of the pebble trap 4 is therefore to eliminatethe high density particles from the spent liquid. Generally, an overflowpipeline 30 is present to allow liquid to be discharged from the well 4should it overflow.

A spent liquid pipeline 10 makes it possible to discharge liquid fromthe well 4. Preferably, this spent liquid pipeline 10 is a spent waterpipeline. It comprises a spent liquid inlet 10in which communicates withthe interior of the well 4 and a spent liquid outlet 10out. The spentliquid pipeline 10 is configured in such a way that liquid can flow fromthe spent liquid inlet 10in to the spent liquid outlet 10out by gravity.In the example shown in FIG. 1, this is possible since the spent liquidoutlet 10out is lower than the spent liquid inlet 10in. This is nothowever necessary. FIG. 2 shows a case where the spent liquid pipeline10 is configured in such a way that liquid can flow from the spentliquid inlet 10in to the spent liquid outlet 10out by gravity without inany way requiring the spent liquid outlet 10out to be lower than thespent liquid inlet 10in. In this case, liquid will pass from the spentliquid inlet 10in to the spent liquid outlet 10out through acommunicating vessel. The arrows indicate the direction of flow of theliquid in the configuration shown in FIG. 2. The force of gravity whichis exerted on the liquid present in the well 4 forces it to flowaccording to the arrows shown in FIG. 2. This spent liquid pipeline 10is therefore equally configured to allow a flow of liquid from the spentliquid inlet 10in to the spent liquid outlet 10out by gravity.

The pumping station 3 of the invention comprises a pumping set 1comprising a first self-priming pump 501. The latter comprises an inlet501in for liquid to be pumped and an outlet 501out for pumped liquid.The pumping set 1 of the invention also comprises a junction pipeline 15comprising a first 15 a and a second 15 b ends. The junction pipeline 15is mechanically coupled (preferably fixed) to the inlet 501in for liquidto be pumped of the first pump 501 by its first end 15 a. Coupling means20 makes it possible to mechanically couple (or link) said junctionpipeline 15 to the spent liquid outlet 10out of the spent liquidpipeline 10 by its second end 15 b. Examples of coupling means 20 are:glue, soldering, a flange, a bend (example represented in FIG. 1), acollar, or any matching part making it possible to link a free end ofthe junction pipeline 15 to the spent liquid outlet 10out of the spentliquid pipeline 10. By virtue of this coupling means 20, liquid can passfrom the spent liquid outlet 10out of the spent liquid pipeline 10 tothe inlet 501in for liquid to be pumped of the first pump 501 withoutpassing through a wet pit. Preferably, the junction pipeline 15 has alength of between two and nine metres. An example of internal diameterfor the junction pipeline 15 is 150 mm. Other internal diameter valuessuch as 80 mm to 300 mm could nevertheless be chosen.

As is illustrated in FIG. 1, the pumping area 8 preferably comprises astabilized 85 to support the spent liquid outlet 10out of the spentliquid pipeline 10. Preferably, this stabilized 85 is made of concrete.Generally, the outlet 501out for pumped liquid of the first pump 501 islinked to a discharge pipeline 45 making it possible to discharge thepumped liquid. Preferably, this discharge pipeline 45 is partlyunderground. As is illustrated in FIG. 1, the first pump 501 ispreferably housed in an enclosure 80 such as a hut.

In a preferred embodiment, the pumping set 1 of the pumping station 3comprises a first 501 and a second 502 pump. A junction pipeline 15makes it possible to link the inlet of the second pump 502 to the spentliquid outlet 10out of the spent liquid pipeline 10. This can be thesame junction pipeline 15 as that used to link the inlet 501in of thefirst pump 501 to the spent liquid outlet 10out of the spent liquidpipeline 10. In another preferred embodiment, each of the first 501 andsecond 502 pumps is rather linked to the spent liquid outlet 10out ofthe spent liquid pipeline 10 by a different junction pipeline (151,152): see FIG. 3. Preferably, these two junction pipelines (151, 152)are then housed in one and the same external pipe 16. Coupling means 20such as a bend for example makes it possible to link each junctionpipeline (151, 152) to the spent liquid outlet 10out of the spent liquidpipeline 10. Either a single coupling means 20 can be used to make thesetwo connections or two different coupling means can be used to link thetwo junction pipelines (151, 152) to the spent liquid outlet 10out ofthe spent liquid pipeline 10.

Preferably, the pumping set 1 (and so the pumping station 3) comprises aregulation system 70 (a programmable logic controller for example) toalternate the operation of the first 501 and second 502 self-primingpumps when said pumping set 1 comprises two such pumps (501, 502). Thismode of operation is illustrated in FIG. 4. This figure shows a timetrend of the state 100 of the first and second pumps (501, 502)according to this preferred mode of operation. The state of the firstpump 501 (respectively second pump 502) is plotted by dotted lines(respectively by solid lines). During one alternation period 5 f, thefirst pump 501 is in operation (state 100 at level 1) while the secondpump 502 is stopped (state 100 at level 0). Then, the reverse applies.

In a preferred embodiment, the pumping set 1 of the pumping station 3comprises a regulation system 70 (a programmable logic controller forexample) to impose the following operation on the first pump 501 (it canbe the same regulation system 70 as that described previously oranother). When a level of liquid to be pumped is h1 or greater, saidregulation system 70 starts said first pump 501 and imposes a pumpingspeed v1 on it. The first pump 501 will therefore be triggered when theliquid level is h1 and will then operate at the pumping speed (or speedof rotation of a centrifugal pump) v1, the time for the first pump 501to be primed and then to provoke a reduction in the liquid level toh2<h1. Preferably, this pumping speed v1 represents the maximum pumpingspeed (or maximum flow rate) of the first pump 501. An example of speedv1 is 1500 rpm. The time for said liquid level to change from h1 to h2depends on the one hand on the priming time (which depends on the speedof the first pump 501) and on the liquid intake flow rate at thatmoment. Preferably, said liquid level represents the level of liquid inthe well 4 (which is preferably a pebble trap). This is illustrated inFIG. 5 which shows two two-dimensional cross sections of the pumping setof the invention according to a preferred embodiment in combination witha spent liquid pipeline 10 and a well 4. Preferably, said liquid levelis measured using a level sensor such as a bubbling sensor (exampleillustrated in FIG. 5). In this case, the level sensor comprises abubbling tube 61, the end 61 a of which is preferably situated inproximity to the spent liquid outlet 10out in the spent liquid pipeline10. Preferably, a zero liquid level then corresponds to a liquid levelwhich is located at the same height as said end 61 a of the bubblingtube 61. A positive liquid level then corresponds to a liquid levelsituated above said end 61 a of the bubbling tube 61; in other words,and from a general point of view, a zero liquid level thereforecorresponds to a liquid level located at the same height as that atwhich the level is measured by the level sensor. The dimensionsmentioned in FIG. 5 and in the subsequent figures are purelyillustrative for certain exemplary preferred embodiments. Otherdimensions can be used.

When said liquid level reaches h2<h1 (see FIG. 6), the regulation system70 imposes a speed on the first pump 501 such that said liquid level iskept constant (therefore at h2) during a time interval ΔT, to within thetolerance of measurement errors and with a liquid level indicationtolerance which is preferably between +/−5%. Preferably, ΔT is fiveminutes. The pumping speed variation of the first pump 501 is preferablymade possible by virtue of the use of one or more variable frequencydrive(s). Preferably, such a variable frequency drive is installed in acontrol unit on the surface of the ground. During ΔT, the flow rate ofthe first pump 501 is equal to the effluent intake flow rate.

Once the time interval ΔT has ended, the regulation system 70 imposes apumping speed v3 on the first pump 501. Preferably, v3 is equal to themaximum pumping speed of the first pump 501. This will enable the firstpump 501 to exceed the effluent intake flow rate and to empty aninclined spent liquid pipeline 10 as illustrated in FIG. 7 to a levelh3. When said liquid level reaches h3, the regulation system 70 stopsthe first pump 501 (h3=0 in FIG. 7). Subsequently, the spent liquidpipeline 10 will be filled once again to the level h1 following theintake of effluent or liquid.

The sequence of operations of the first pump 501 imposed by theregulation system 70 which has just been described in relation to FIGS.5 to 7 allows for the self-clearing of an inclined spent liquid pipeline10 by carrying away floats and decantations. The stopping of the firstpump 501 at the level h3 makes it possible to avoid the introduction ofair during the pumping, which is damaging to the pumps. The pumping ofliquid and air initiates significant vibrations of the pump and canresult in premature mechanical breakdowns of the mechanical bearings andpackings. At the end of the sequence of operations of the first pump501, it was stated that the spent liquid pipeline 10 will be filled onceagain to the level h1 following the intake of effluent or liquid. It isthen possible to repeat this sequence of operations. In anotherpreferred embodiment, this sequence will be imposed rather on a secondpump 502 when the pumping set 1 comprises at least two pumps. The latterwill then complete the same cycle of operations as described previously.This makes it possible to have the first 501 and second 502 pumps wearin the same way. This makes it easier to schedule pump maintenance.

Preferably, the following procedure is chosen for monitoring themalfunctioning of the first 501 and second 502 pumps when the pumpingset 1 of the pumping station 3 comprises two such pumps. This monitoringprocedure can be applied by a regulation system 70, for example, thesame as that described previously in relation to FIGS. 5 to 7. In thisprocedure, there are two additional thresholds for the liquid level,which preferably represents a level of liquid in a well 4 upstream ofthe spent liquid pipeline 10 (see above): h4 and h5. The threshold h4 issuch that h4>h1 in an upward vertical direction. Preferably, h4 issituated at a vertical distance from h1 of between 20 and 80 cm. Evenmore preferably, h4=h1+40 cm. To illustrate the monitoring procedure forwhich the associated liquid levels are shown in FIGS. 8 and 9, it isassumed that the first pump 501 is in operation to pump liquid but thatthe second pump 502 is stopped (the monitoring procedure neverthelessapplies in the contrary case, mutatis mutandis). When a liquid levelreaches h4, the second pump 502 is started, whereas the first pump 501is stopped. This procedure is followed because, if a level h4 isreached, that means that the first pump 501 is not giving its nominalflow rate. Simultaneously with the stopping of the first pump 501, analarm is triggered. Subsequently, the second pump 502 is the only one tooperate pending the intervention of a maintenance department which willhave to intervene on the first pump 501 to repair it. It may be that thefirst 501 and second 502 pumps are both damaged. In this case, theliquid level will continue to rise up to a high general alarm levelcalled h5. Preferably, this level h5 corresponds to the overflow levelof a well 4. When the liquid reaches this overflow level, the liquid canpreferably flow through an overflow pipeline 30, see for example in FIG.9. Preferably, an alarm is generated when the liquid level reaches h5.Thus, the users can be alerted thereof. Preferably, the following valuesare used for h1 to h5: h1=80%, h2=40%, h3=0%, h4=90%, and h5=100%.

Preferably, the pumping set 1 (and so the pumping station 3) comprises abypass pipeline 50 (see FIGS. 5 to 9). The bypass pipeline 50 can, forexample, be a DN50, DN65 or DN80 tube (DN denotes the nominal diameterwhich is a concept known to those skilled in the art). The choice of aparticular type will depend on the size and the pumping power of thefirst pump 501. This bypass pipeline 50 is mechanically coupled to thefirst pump 501. More specifically, the bypass pipeline 50 is connectedto the pumped liquid outlet 501out of the first pump 501. In a preferredembodiment comprising two pumps, the bypass pipeline 50 ispreferentially connected to both pumps: in this preferred variant, thereis therefore a bypass pipeline 50 for both pumps. It is, however,possible to provide two bypass pipelines 50, one for each pump (501,502).

Hereinafter in the description of the preferred embodiment comprising abypass pipeline 50, it will be assumed that there is only a single pump,called first pump 501. The elements described below nevertheless applyto a preferred embodiment comprising two pumps (501, 502). Preferably, avalve is inserted between the outlet for pumped liquid 501out of thefirst pump 501 and the bypass pipeline 50. The latter can have threefunctions.

The bypass pipeline 50 can be used to discharge air when the firstself-priming pump 501 is priming. In practice, when the first pump 501creates the vacuum in the suction piping (that is to say in particularthe junction pipeline 15) for the atmospheric pressure to be able tothen push the liquid to be pumped into the suction piping, the suckedair has to be discharged. The bypass pipeline 50 can be used todischarge this sucked air during the priming.

Also, the bypass pipeline 50 can be used to clean a part of the liquidcircuit, for example an internal region of the spent liquid pipeline 10.In normal use of the first pump 501, the valve situated between theoutlet for pumped liquid 501out of the first pump 501 and the bypasspipeline 50 is closed, preventing the passage of liquid into thispipeline. When the user wants, he or she can open this valve while thefirst pump 501 is operating. At least a portion of pumped liquid whichis under pressure is outgoing from the outlet for pumped liquid 501outis then diverted to this bypass pipeline 50 and is driven to the placewhere the end of the bypass pipeline 50 which is not connected to thefirst pump 501 is located. This point corresponds, for example, to aninternal region of the spent liquid pipeline 10, in proximity to thespent liquid outlet 10out (that is to say, in a region situated at adistance less than 35 cm from said spent liquid outlet 10out along themain axis of the spent liquid pipeline 10). Sand and decanted particlescan therefore be returned to suspension while continuing to pump. Thisfunction is very effective since it takes its feed immediately at thedischarge (or at the outlet) of the pumps (at the point where thepressure is maximum). The valve situated between the outlet for pumpedliquid 501out of the first pump 501 and the bypass pipeline 50 can bemanual or automatic, electric for example. An electric automatic valvecan be opened via a regulation system 70 or a control system such as aprogrammable logic controller for example. Such a programmable logiccontroller can be housed in the electrical cabinet which is located onthe surface of the ground, in proximity to the pump or pumps (501, 502).Preferably, the valve is open two minutes every hour.

Finally, when the pump or pumps is/are stopped, the bypass pipeline 50can be opened (via the valve described above for example) by the user todrain the entire discharge column (located downstream of the outlet forpumped liquid 501 of the pumps) in order, for example, to carry out amaintenance intervention on the discharge duct (which can sometimes beseveral kilometres).

Preferably, the pumping set 1 (and so the pumping station 3) of theinvention comprises a discharge non-return valve between the outlet forpumped liquid 501 of the pump or pumps and the discharge pipeline(s)through which the pumped liquid is discharged. Such a valve makes itpossible to avoid, on the one hand, water hammer, and, on the otherhand, having the discharge column empty when the pump or pumps is/arestopped.

Preferably, the pumping set 1 (and so the pumping station 3) of theinvention comprises an air venting valve between the pump or pumps (501,502) and said discharge non-return valve. This air venting valve isclosed automatically when the pump or pumps (501, 502) is/are primed byvirtue of the pressure that the pumped liquid then exerts at this level.

Preferably, the end 50 a of the bypass pipeline 50 which is notconnected to an outlet for pumped liquid 501out of a pump is immersed ina bottom part of the spent liquid pipeline 10 which generally comprisesliquid: see for example FIGS. 5 to 9. This makes it possible to avoidthe unpriming of the pump or pumps once stopped. In practice, since thispiping is immersed, air cannot reenter into it. Also, the dischargenon-return valve also prevents the ingress of air into the piping.

Preferably, the pumping set 1 (and so the pumping station 3) comprises alevel sensor for measuring a liquid level. Preferably, this liquid levelrepresents a level of liquid in the spent liquid pipeline 10. It canalso, in another preferred variant, be a level of liquid in a well 4(for example a pebble trap) upstream of the spent liquid pipeline 10. Itis then possible to regulate the pump or pumps by knowing such a leveland applying a closed loop regulation. Preferably, said level sensor isa bubbling level sensor comprising a bubbling tube 61. This type ofsensor is known to those skilled in the art. Preferably, the bubblingtube 61 is a DN25 pipe. Preferably, two level sensors such as twobubbling sensors are used in order to increase the reliability of theliquid level measurement. Compressed air is injected into the bubblingtube or tubes 61 (for example at a rate of one bubble per second) bymeans of a bubble-maker which is preferably situated on the surface ofthe ground, for example inside a but housing the pump or pumps (501,502). One end of the bubbling tube(s) 61 is preferably positioned in thespent liquid pipeline 10 as is illustrated in FIGS. 5 to 9, preferablyat a distance less than 35 cm from the spent liquid outlet 10out of saidspent liquid pipeline 10. This distance is preferably measured along themain axis of the spent liquid pipeline 10. When said spent liquidpipeline 10 is in the form of a hollow cylinder, this main axiscorresponds to the axis of revolution of said hollow cylinder.Preferably, the bubbling tube(s) 61 is/are terminated by bubbling bellsat the end located in the spent liquid pipeline 10.

The spent liquid pipeline 10 of the pumping station 3 of the inventiongenerally takes the form of a hollow cylinder. Preferably, the spentliquid pipeline 10 is linked to a well 4 such as a pebble trap (see FIG.1). In another preferred embodiment, the spent liquid pipeline 10 isdirectly linked to a recovery pipeline 40 (see FIG. 11). In this case,the use of a well 4 such as a pebble trap is not necessary. Theinventors therefore also propose the following original set: the pumpingstation 3 according to the invention, and one or more recovery pipelines40, such that the spent liquid pipeline 10 of the pumping station 3 isdirectly linked to the recovery pipeline(s) 40. Then, liquid can flowdirectly from the recovery pipeline(s) 40 to the first pump 501 withoutpassing by a well (4) (pebble trap for instance) or by a wet pit.

Preferably, the spent liquid pipeline 10 has a mean inclination 11 ofbetween 10° and 50° (with an even more preferred value of 45°) relativeto a horizontal plane such that said spent liquid inlet 10in is situatedat a greater (or higher) level relative to the spent liquid outlet 10outin a vertical direction. This is illustrated in FIG. 10 for a preferredembodiment in which the spent liquid pipeline 10 takes the form of ahollow cylinder. In such a case, the corresponding axis of revolution(shown in broken lines in FIG. 10) has an inclination 11 of between 10°and 50° (with an even more preferred value of 45°) relative to ahorizontal plane in this preferred embodiment. In FIGS. 5 to 9, thespent liquid pipeline 10 has a mean inclination 11 of 30° relative to ahorizontal plane.

Preferably, the spent liquid pipeline 10 is located underground andmakes it possible to pour water by gravity from a well 4 (pebble trapfor example). Preferably, the pump(s) is/are located on the surfacewhich means that they can be easily accessed, which makes theirmaintenance easier. These preferred variants are illustrated in FIG. 1in which the reference sign 2 represents the ground.

Preferably, when the pumping station 3 comprises a first 501 and asecond 502 pump, they are suitable for operating alternately with analternation period 5 f of between four and six minutes, including a morepreferred value of five minutes. To this end, the pumping station 3preferentially comprises a regulation system 70 as described previously,making it possible to control said first 501 and a second 502 pump inthis way.

Preferably, the pumping station 3 comprises a bypass pipeline 50. Thisbypass pipeline 50 is linked to the first pump 501 by one of its ends.The other end of the bypass pipeline 50 is preferably situated in thespent liquid pipeline 10, preferably at a distance less than 35 cm fromthe spent liquid outlet 10out. This distance is preferably measuredalong the main axis of the spent liquid pipeline 10. When the spentliquid pipeline 10 is in the form of a hollow cylinder, its main axiscorresponds to the axis of revolution of the hollow cylinder (see dashedinclined line of FIG. 10).

Preferably, the pumping station 3 comprises a level sensor for measuringa liquid level. Preferably, this liquid level is the level of liquid ina well 4 such as a pebble trap to which the spent liquid inlet 10in ofthe spent liquid pipeline 10 is linked. Preferably, this level sensor isa bubbling level sensor. In this preferred variant, the bubbling tube 61is preferably positioned in the spent liquid pipeline 10 in such a waythat one of its ends is situated in proximity to the spent liquid outlet10out of the spent liquid pipeline 10, for example at less than 35 cmfrom said spent liquid outlet 10out. This distance is preferablymeasured along the main axis of the spent liquid pipeline 10. When thespent liquid pipeline 10 is in the form of a hollow cylinder, its mainaxis corresponds to the axis of revolution of the hollow cylinder (seedashed inclined line of FIG. 10).

According to another aspect, the invention relates to a pumping area 8comprising a pumping station as described previously. This pumping area8 can comprise any preferred embodiment of the pumping station describedpreviously. An exemplary pumping area 8 is illustrated in FIG. 1. Inanother preferred example, the pumping area 8 does not comprise a well 4such as a pebble trap (see FIG. 11). In this last case, the spent liquidpipeline 10 is connected directly to the recovery pipeline 40. Thismakes it possible to reduce the bulk and the manufacturing costs. Such apumping area 8 is also simpler to construct and can be constructed inmore different places because there is no need to provide the space forsuch a well 4.

When the pumping area 8 comprises a well 4, the inventors propose thefollowing preferred embodiment. The inventors propose that the bottomsurface 4 b of the well is inclined with respect to a horizontal plane(see FIG. 12). Preferably, the mean inclination or slope of the bottomsurface 4 b of the well is then comprised between 10° and 50°, with apreferred value equal to 30°. This preferred embodiment is preferablyused when the well 4 is a manhole. This preferred embodiment allows aneven better self cleaning and clearing of the pumping area 8.

The inventors also propose, according to another preferred embodiment,to position the spent liquid pipeline 10 such that its spent liquidinlet 10in is located at the bottom of the well 4 that is preferably amanhole in this case (see FIG. 12). This preferred embodiment furtherallows a better self cleaning and clearing of the well 4, and so of thepumping area 8. When this preferred embodiment is used, the well 4 ispreferably a manhole.

The invention also relates to a method for pumping liquid from a spentliquid pipeline 10 as described previously. The inventors proposemechanically coupling (or fixing, linking), for example using glue,soldering or a collar, a junction pipeline 15 between the spent liquidoutlet 10out of said spent liquid pipeline 10 and the inlet for liquidto be pumped 501in of a first self-priming pump 501. This makes itpossible to form a passage for liquid to be pumped from the spent liquidpipeline 10 to the inlet for liquid to be pumped 501in of the first pump501 without having to pass through a wet pit.

The preferred embodiments described in relation to the pumping station 3of the invention apply for the method of the invention, mutatismutandis. This means that the method of the invention enjoys the sameadvantages. Thus, it is, for example, possible to link a first 501 and asecond 502 self-priming pump to the spent liquid outlet 10out of a spentliquid pipeline 10 by using one or more junction pipeline(s) (15; 151,152).

The present invention has been described in relation to specificembodiments, which have a purely illustrative value and should not beconsidered to be limiting. Generally, it will appear evident to a personskilled in the art that the present invention is not limited to theexamples illustrated and/or described above. The presence of referencenumbers in the drawings cannot be considered to be limiting, includingwhen these numbers are indicated in the claims. The use of the verbs“comprise”, “include” or any other variant, and their conjugations,cannot in any way preclude the presence of elements other than thosementioned. The use of the indefinite article “a”, “an”, or of thedefinite article “the”, to introduce an element does not preclude thepresence of a plurality of these elements.

The invention can also be described as follows. Method for pumpingliquid from a spent liquid pipeline and comprising the steps of:providing a first pump, providing a junction pipeline, mechanicallycoupling said junction pipeline to said first pump and to said spentliquid pipeline for allowing liquid to flow from said spent liquidpipeline to said first pump. The method is characterized in that saidfirst pump 501 is a self-priming pump.

1. A method for pumping liquid from a spent liquid pipeline, said spentliquid pipeline comprising a spent liquid inlet and a spent liquidoutlet and configured in such a way that said liquid can flow from saidspent liquid inlet to said spent liquid outlet by gravity, said methodcomprising the following steps: providing a first pump for pumping saidliquid, comprising an inlet for liquid to be pumped and an outlet forpumped liquid; providing a junction pipeline comprising a first and asecond end; mechanically coupling said first end of said junctionpipeline to said inlet of said first pump and mechanically coupling saidsecond end of said junction pipeline to said spent liquid outlet of saidspent liquid pipeline such that said inlet for liquid to be pumped ofsaid first pump is connected to said spent liquid pipeline via saidjunction pipeline; wherein said first pump is a self-priming pump. 2.The method according to claim 1, wherein said spent liquid pipeline isan underground pipeline.
 3. The method according to claim 2, whereinsaid underground spent liquid pipeline is a pipeline for dischargingspent liquid from a well.
 4. The method according to claim 3, whereinsaid well is a pebble trap.
 5. The method according to claim 1, whereinit comprises a step of positioning the spent liquid pipeline such thatit has a mean inclination of between 10° and 50° relative to ahorizontal plane such that said spent liquid inlet is situated at ahigher level relative to said spent liquid outlet in a verticaldirection.
 6. The method according to claim 5, wherein it comprises astep of positioning the spent liquid pipeline such that it has a meaninclination of between 30° and 45° relative to a horizontal plane suchthat said spent liquid inlet is situated at a higher level relative tosaid spent liquid outlet in a vertical direction.
 7. The methodaccording to claim 1, wherein it comprises a step of positioning saidfirst pump on the surface of the ground.
 8. The method according toclaim 1, wherein said first pump is controlled as follows: when a levelof liquid to be pumped is h1 or greater, starting said first pump andimposing a pumping speed v1≠0 on it; if said liquid level is greaterthan h2<h1 but less than or equal to h1, imposing said pumping speed v1on said first pump if the latter is in operation; when said liquid levelreaches h2<h1, imposing a pumping speed v2<v1 on said first pump duringa time interval ΔT, such that said liquid level is kept constant; aftersaid time interval ΔT, imposing a pumping speed v3 on said first pumpsuch that said liquid level reaches a value h3<h2; when said liquidlevel reaches h3<h2, stopping the first pump.
 9. A pumping stationcomprising: a spent liquid pipeline comprising a spent liquid inlet anda spent liquid outlet, and configured in such a way that liquid can flowfrom said spent liquid inlet to said spent liquid outlet by gravity, apumping set for pumping liquid from said spent liquid pipeline andcomprising: a first pump for pumping said liquid, comprising an inletfor liquid to be pumped and an outlet for pumped liquid; a junctionpipeline mechanically coupled to said inlet of said first pump; couplingmeans mechanically coupled to said junction pipeline and suitable formechanically coupling said junction pipeline to said spent liquid outletof said spent liquid pipeline, said pumping station being configuredsuch that said spent liquid pipeline is mechanically coupled to saidjunction pipeline by said coupling means, allowing a flow of spentliquid from the spent liquid inlet of said spent liquid pipeline to itsspent liquid outlet then to said junction pipeline and then to saidinlet for liquid to be pumped of said first pump when the latter isoperating; wherein said first pump is a self-priming pump.
 10. Thepumping station according to claim 9, wherein the spent liquid pipelinehas a mean inclination of between 10° and 50° relative to a horizontalplane such that said spent liquid inlet is situated at a higher levelrelative to said spent liquid outlet in a vertical direction.
 11. Thepumping station according to claim 9, wherein the spent liquid pipelinehas a mean inclination of between 30° and 45° relative to a horizontalplane such that said spent liquid inlet is situated at a higher levelrelative to said spent liquid outlet in a vertical direction.
 12. Thepumping station according to claim 9, wherein: said spent liquidpipeline is located underground, and wherein said first pump is locatedon the surface of the ground.
 13. The pumping station according to claim9, wherein said pumping set comprises: a self-priming second pump forpumping said liquid, comprising an inlet for liquid to be pumped and anoutlet for pumped liquid; a junction pipeline mechanically coupled tosaid inlet of said second pump; coupling means mechanically coupled tosaid junction pipeline and suitable for mechanically coupling saidjunction pipeline to said spent liquid outlet of said spent liquidpipeline.
 14. The pumping station according to claim 13 wherein itcomprises a regulation system for alternating the operation of saidfirst and second pumps.
 15. The pumping station according to claim 9,wherein said junction pipeline has a length of between two and ninemetres.
 16. The pumping station according to claim 9, wherein itcomprises a regulation system for controlling the operation of saidfirst pump as follows: when a level of liquid to be pumped is h1 orgreater, said regulation system is suitable for starting said first pumpand imposing a pumping speed v1 on it; when said liquid level is greaterthan h2<h1 but less than or equal to h1, said regulation system issuitable for imposing said pumping speed v1 on said first pump; whensaid liquid level reaches h2<h1, said regulation system is suitable forimposing a pumping speed v2 on said first pump such that v2<v1 during atime interval ΔT such that said liquid level is kept constant; aftersaid time interval ΔT, said regulation system is suitable for imposing apumping speed v3 on said first pump such that said liquid level reachesa value h3<h2; when said liquid level reaches h3<h2, said regulationsystem is suitable for stopping said first pump.
 17. The pumping stationaccording to claim 16 wherein said pumping speeds v1 and v3 are equal tothe maximum pumping speed of said first pump.
 18. The pumping stationaccording to claim 9 wherein it comprises a bypass pipeline coupled tosaid first pump to allow for cleaning of a region situated in said spentliquid pipeline by diverting at least a portion of liquid pumped by saidfirst pump to said region.
 19. The pumping station according to claim 9wherein it comprises a level sensor for measuring a liquid level. 20.The pumping station according to claim 19 wherein said liquid level is aliquid level in said spent liquid pipeline.
 21. The pumping stationaccording to claim 19 wherein said level sensor is a bubbling levelsensor comprising a bubbling tube.
 22. A pumping area comprising thepumping station according to claim 9 and a well, said spent liquid inletof said spent liquid pipeline being in communication with the interiorof said well.
 23. The pumping area according to claim 22, wherein saidwell is a pebble trap.